Websites/Books I recommend for more in depth at personality type theory, INFP, and other personality types.
16 Personalities: http://www.16personalities.com/
Cognitive Processes: http://www.cognitiveprocesses.com/
Personality Junkie: http://personalityjunkie.com/
Introvert, Dear: http://introvertdear.com/
A Little Bit of Personality: http://www.alittlebitofpersonality.com/p/start-here.html
Oddly Developed Types: http://oddlydevelopedtypes.com/
Please Understand Me II: http://www.amazon.com/Please-Understand-Me-David-Keirsey-ebook/dp/B004O0U1GU/ref=pd_ybh_17